Controlling access point transmit power based on event-triggered access terminal messaging

ABSTRACT

Transmit power for an access point is controlled based on measurement reports received by the access point from one or more access terminals that are not currently being served by the access point. In some aspects, transmit power is controlled based on the number of received messages that correspond to a particular event. In some aspects, transmit power is controlled based on the contents of the received messages. For example, the access point may use signal strength information included in the messages to determine a level of transmit power that mitigates interference at a defined subset of reporting access terminals.

CLAIM OF PRIORITY

This application claims the benefit of and priority to commonly ownedU.S. Provisional Patent Application No. 61/306,885, filed Feb. 22, 2010,and assigned Attorney Docket No. 101067P1, the disclosure of which ishereby incorporated by reference herein.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to concurrently filed and commonly ownedU.S. patent application Ser. No. ______, entitled “CONTROLLING ACCESSPOINT TRANSMIT POWER BASED ON ACCESS TERMINAL RANKING,” and assignedAttorney Docket No. 101067U2, the disclosure of which is herebyincorporated by reference herein.

BACKGROUND

1. Field

This application relates generally to wireless communication and morespecifically, but not exclusively, to controlling access point transmitpower.

2. Introduction

A wireless communication network may be deployed over a geographicalarea to provide various types of services (e.g., voice, data, multimediaservices, etc.) to users within that geographical area. In a typicalimplementation, macro access points (e.g., each of which providesservice via one or more cells) are distributed throughout a macronetwork to provide wireless connectivity for access terminals (e.g.,cell phones) that are operating within the geographical area served bythe macro network.

As the demand for high-rate and multimedia data services rapidly grows,there lies a challenge to implement efficient and robust communicationsystems with enhanced performance. To supplement conventional networkaccess points (e.g., to provide extended network coverage),small-coverage access points (e.g., low power access points) may bedeployed to provide more robust indoor wireless coverage or othercoverage to access terminals inside homes, enterprise locations (e.g.,offices), or other locations. Such small-coverage access points may bereferred to as, for example, femto cells, femto access points, HomeNodeBs, Home eNodeBs, or access point base stations. Typically, suchsmall-coverage access points are connected to the Internet and themobile operator's network via a DSL router or a cable modem. Forconvenience, small-coverage access points may be referred to as femtocells or femto access points in the discussion that follows.

In a co-channel or shared carrier deployment of femto cells such as HomeNode Bs, there is a need to protect non-Closed Subscriber Group accessterminals (also denoted as non-allowed access terminals or macro accessterminals) from interference from Home NodeBs by limiting the transmitpower of the Home NodeBs for pilot, overhead, data, and other channels.This transmit power control may be referred to as Home NodeB powercalibration. One goal of a transmit power calibration algorithm is tostrike a balance between Home NodeB coverage provided to served accessterminals (e.g., home access terminals) and limiting the interferenceimpact on non-served access terminals (e.g., macro access terminals orother femto access terminals).

Some conventional transmit power calibration schemes are based onmeasurements made by a downlink receiver (e.g., a Network Listen Module)at the Home NodeB. This calibration is based on the assumption thatnearby home access terminals and nearby macro access terminals will seethe same or similar RF conditions as the Network Listen Module. Thisassumption is not fully accurate, however. Consequently, Network ListenModule-based transmit power calibration suffers from two mismatchconditions.

First, there may be an RF mismatch condition. For example, a Home NodeBplaced near a window may see significantly higher macro interferencethan a home access terminal which may be predominantly away from thewindow. As another example, a Home NodeB placed in a basement may seesignificantly lower macro interference than a home access terminal whichis predominantly in a higher floor.

Second, there may a deployment mismatch condition. For example, theNetwork Listen Module is unaware of the macro access terminal trafficsurrounding the Home NodeB deployment. A Home NodeB deployed near a busystreet corner in a small apartment may affect more macro accessterminals than one deployed deep inside a suburban home. This mismatchcreates an inaccurate power setting for the Home NodeB in the sense thatthe power setting may create too much interference for macro users. Thisinterference could lead to excessive inter-frequency handovers or calldrops (e.g., when the Home NodeB is placed near a window or near a busystreet corner) or could result in inadequate coverage for home accessterminals (e.g., when the Home NodeB is placed in a basement or when theHome NodeB is used in a ranch house).

In view of the above, there is a need for effective techniques forprotecting macro cell users and other non-allowed users frominterference from femto cells while still providing adequate coveragefor allowed femto cell users.

SUMMARY

A summary of several sample aspects of the disclosure follows. Thissummary is provided for the convenience of the reader and does notwholly define the breadth of the disclosure. For convenience, the termsome aspects may be used herein to refer to a single aspect or multipleaspects of the disclosure.

The disclosure relates in some aspects to controlling transmit power ofan access point. In particular, transmit power for an access point maybe controlled based on measurement reports received by the access pointfrom one or more access terminals that are not currently being served bythe access point (e.g., access terminals that are in an active call withanother access point or that are in idle mode). Such a scheme may beused, for example, to provide transmit power calibration for a femtocell that is operating on a carrier shared with macro access pointsand/or other femto cells. By effectively learning the boundaries of thefemto cell deployment based on received measurement reports, the femtocell may configure its transmit power to limit the number of non-servedaccess terminals (e.g., macro access terminals) affected by interferencefrom the femto cell. Advantageously, such a measurement report-basedscheme may mitigate (e.g., eliminate) RF mismatch conditions and/ordeployment mismatch conditions that may otherwise exist in a NetworkListen Module-based calibration scheme.

The disclosure relates in some aspects to controlling transmit powerbased on the number of measurement report messages corresponding to aparticular event that are received by an access point. In some aspects,an event-based transmit power control scheme may involve: receivingmessages at an access point, wherein the messages comprise measurementreports from at least one access terminal that is not currently beingserved by the access point; identifying a quantity of the messages thatindicate the occurrence of a specified type of event; comparing thequantity to a threshold; and controlling transmit power of the accesspoint based on the comparison.

The disclosure relates in some aspects to controlling transmit powerbased on the contents of received measurement report messages. Forexample, an access point may use signal strength information included inthe messages to rank reporting access terminals and determine a level oftransmit power that mitigates interference at a defined subset of thereporting access terminals. In some aspects, a ranking-based transmitpower control scheme may involve: receiving messages at an access point,wherein the messages comprise measurement reports from a plurality ofaccess terminals that are not currently being served by the accesspoint; ranking the access terminals based on the received messages,wherein the ranking corresponds to signal conditions at the accessterminals that result from transmissions by the access point;designating a subset of the access terminals based on the ranking; andcontrolling transmit power of the access point to achieve specifiedsignal conditions at the subset of access terminals.

The disclosure relates in some aspects to a network entity that sendsmeasurement reports to an access point that controls transmit powerbased on received measurement reports. In some aspects, a measurementreport handling scheme may involve: receiving measurement reports at anetwork entity, wherein each of the measurement reports correspond to aspecified (i.e., the same) access point; determining that the specifiedaccess point controls transmit power based on measurement reports; andsending the measurement reports to the specified access point as aresult of the determination.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other sample aspects of the disclosure will be described inthe detailed description and the appended claims that follow, and in theaccompanying drawings, wherein:

FIG. 1 is a simplified block diagram of several sample aspects of acommunication system wherein an access point controls its transmit powerbased on access terminal measurement reports;

FIG. 2 is a flowchart of several sample aspects of operations that maybe performed in conjunction with controlling transmit power of an accesspoint based on access terminal measurement reports;

FIG. 3 is a flowchart of several sample aspects of operations that maybe performed in conjunction with controlling transmit power of an accesspoint based on event-triggered measurement reports;

FIG. 4 is a flowchart of several sample aspects of operations that maybe performed in conjunction with controlling transmit power of an accesspoint based on a ranking of access terminal measurement reports;

FIG. 5 is a flowchart of several sample aspects of operations that maybe performed in conjunction with a handling measurement reports at anetwork entity;

FIG. 6 is a simplified block diagram of several sample aspects of acommunication system wherein an access point uses a multi-stage powercontrol scheme to control transmit power;

FIG. 7 is a flowchart of several sample aspects of operations that maybe performed in conjunction with a multi-stage transmit power controlscheme;

FIG. 8 is a simplified block diagram of several sample aspects ofcomponents that may be employed in communication nodes;

FIG. 9 is a simplified diagram of a wireless communication system;

FIG. 10 is a simplified diagram of a wireless communication systemincluding femto nodes;

FIG. 11 is a simplified diagram illustrating coverage areas for wirelesscommunication;

FIG. 12 is a simplified block diagram of several sample aspects ofcommunication components; and

FIGS. 13-15 are simplified block diagrams of several sample aspects ofapparatuses configured to control transmit power as taught herein.

In accordance with common practice the various features illustrated inthe drawings may not be drawn to scale. Accordingly, the dimensions ofthe various features may be arbitrarily expanded or reduced for clarity.In addition, some of the drawings may be simplified for clarity. Thus,the drawings may not depict all of the components of a given apparatus(e.g., device) or method. Finally, like reference numerals may be usedto denote like features throughout the specification and figures.

DETAILED DESCRIPTION

Various aspects of the disclosure are described below. It should beapparent that the teachings herein may be embodied in a wide variety offorms and that any specific structure, function, or both being disclosedherein is merely representative. Based on the teachings herein oneskilled in the art should appreciate that an aspect disclosed herein maybe implemented independently of any other aspects and that two or moreof these aspects may be combined in various ways. For example, anapparatus may be implemented or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented or such a method may be practiced using otherstructure, functionality, or structure and functionality in addition toor other than one or more of the aspects set forth herein. Furthermore,an aspect may comprise at least one element of a claim.

FIG. 1 illustrates several nodes of a sample communication system 100(e.g., a portion of a communication network). For illustration purposes,various aspects of the disclosure will be described in the context ofone or more access terminals, access points, and network entities thatcommunicate with one another. It should be appreciated, however, thatthe teachings herein may be applicable to other types of apparatuses orother similar apparatuses that are referenced using other terminology.For example, in various implementations access points may be referred toor implemented as base stations, NodeBs, eNodeBs, Home NodeBs, HomeeNodeBs, macro cells, femto cells, and so on, while access terminals maybe referred to or implemented as user equipment (UEs), mobiles, and soon.

Access points in the system 100 provide access to one or more services(e.g., network connectivity) for one or more wireless terminals (e.g.,access terminals 102 and 104) that may be installed within or that mayroam throughout a coverage area of the system 100. For example, atvarious points in time the access terminal 102 may connect to an accesspoint 106, an access point 108, or some access point in the system 100(not shown). Similarly, at various points in time the access terminal104 may connect to the access point 108 or some access point in thesystem 100.

Certain types of access points (e.g., femto cells) may be configured tosupport different types of access modes. For example, in an open accessmode, an access point may allow any access terminal to obtain any typeof service via the access point. In a restricted (or closed) accessmode, an access point may only allow authorized access terminals toobtain service via the access point. For example, an access point mayonly allow access terminals (e.g., so called home access terminals)belonging to a certain subscriber group (e.g., a closed subscriber group(CSG)) to obtain service via the access point. In a signaling-only (orhybrid) access mode, alien access terminals (e.g., non-home accessterminals, non-CSG access terminals) may only be allowed to obtainsignaling access via the access point. For example, a macro accessterminal that does not belong to a femto cell's CSG may be allowed toperform certain paging, registration, and other signaling operations atthe femto cell, but may not be allowed to obtain active mode service viathe femto cell.

Each of the access points may communicate with one or more networkentities (represented, for convenience, by a network entity 110) tofacilitate wide area network connectivity. These network entities maytake various forms such as, for example, one or more radio and/or corenetwork entities. Thus, in various implementations the network entitiesmay represent functionality such as at least one of: network management(e.g., via an operation, administration, management, and provisioningentity), call control, session management, mobility management, gatewayfunctions, interworking functions, or some other suitable networkfunctionality. Also, two of more of these network entities may beco-located and/or two or more of these network entities may bedistributed throughout a network.

The access point 106 (e.g., a femto cell) provides service for nearbyaccess terminals through the use of a service channel that operates on adesignated carrier frequency. In some cases (e.g., co-channeldeployments), this carrier frequency may be used by different types ofaccess points (e.g., femto cells and macro cells). In other cases,different types of access points may operate on different carrierfrequencies. For example, femto cells may deploy their service channelson a dedicated femto carrier frequency, while macro cells may deploytheir service channels on one or more macro carrier frequencies. In thelatter case, a femto cell may transmit beacons on each macro carrierfrequency to enable nearby access terminals operating on that carrierfrequency to find the femto cell. Thus, in either a co-channel or anon-co-channel deployment scenario, transmissions by a femto cell on agiven carrier frequency may interfere with signal reception at a nearbyaccess point that is in active communication with another access point(e.g., a macro cell or another femto cell).

The potentially interfering transmissions by an access point may takevarious forms. For example, in a co-channel deployment, a femto cell'sforward link transmissions (e.g., for the service channel) may causeinterference at nearby macro access terminals operating on the samecarrier frequency. As another example, in a deployment where a femtocell transmits beacons on a macro carrier frequency, these beacontransmissions may cause interference at nearby macro access terminalsoperating on that macro carrier frequency. In some implementations, anaccess point transmits beacons at different power levels. Here, theaccess point will normally transmit beacons at a low power level in anattempt to minimize interference caused by the beacons. However, theaccess point will regularly transmit beacons at a higher power level (ormultiple higher levels) for short periods of time to facilitateattracting access terminals from a greater distance.

The access point 106 employs transmit power control to provide a desiredarea of communication coverage for attracting and/or communicating withaccess terminals (e.g., the access terminal 102) that are authorized toreceive active mode service from the access point 106, while mitigatinginterference that transmissions by the access point 106 may have onnearby access terminals (e.g., the access terminal 104) that are notcurrently being served by (e.g., not authorized to receive active modeservice from) the access point 106. For example, the access terminal 102may be a member of a CSG of the access point 106 while the accessterminal 104 is not a member of that CSG. In this case, it is desirablefor the access point 106 to use sufficient transmit power (e.g., forbeacon and/or forward link transmissions) so that the access terminal102 is able to detect the presence of the access point 106 and/orcommunicate with the access point 106 from a particular distance (e.g.,throughout a building within which the access point 106 is deployed).Conversely, it is preferable that the transmissions by the access point106 do not unduly interfere with the ability of the access terminal 104to receive signals from the access point 108 (e.g., a serving macro cellfor the access terminal 104).

In accordance with the teachings herein, the access point 106 employs atransmit power control scheme that is based on measurement reports fromone or more access terminals that are not currently being served by theaccess point 106. Through the use of such a scheme, calibration ofaccess point transmit power may be achieved in a manner that takes intoaccount deployment-specific scenarios such as the size of the buildingwithin which the access point is deployed and the number of affectednon-served access terminals (e.g., non-allowed access terminals such asmacro access terminals) in the vicinity of the access point.Consequently, a better tradeoff may be achieved between coverage of anaccess point (e.g., a closed femto cell) and interference to non-servedaccess terminals. An example of messaging operations that may beperformed in conjunction with such a transmit power control scheme willnow be described in conjunction with FIG. 2.

For convenience, the operations of FIG. 2 (or any other operationsdiscussed or taught herein) may be described as being performed byspecific components (e.g., the components of FIG. 1 and FIG. 8). Itshould be appreciated, however, that these operations may be performedby other types of components and may be performed using a differentnumber of components. It also should be appreciated that one or more ofthe operations described herein may not be employed in a givenimplementation.

As represented by block 202 of FIG. 2, at various points in time, theaccess terminal 104 receives RF signals (e.g., forward link signals,pilot signals) from nearby access points and measures the receivedsignal quality of these RF signals. The access points from which theseRF signals are received will include the access point (e.g., the accesspoint 108) currently serving the access terminal 104 and may includeother access points (e.g., the access point 106) that are not currentlyserving the access terminal 104.

As represented by block 204, the access terminal 104 generatesmeasurement report messages based on the RF signal measurements andsends these messages to its serving access point 108. For example, anaccess terminal may be configured or requested to provide periodic orevent-triggered measurement report messages (MRMs) to its serving accesspoint (e.g., a serving base station) or to some other network entity(e.g., a radio network controller).

In some aspects, these measurement reports convey the radio conditionsand surrounding access points seen by the access terminal. That is, ameasurement report provides an indication of the identity of eachobserved access point and provides an indication of the received signalquality of RF signals measured at the access terminal 104. For example,a measurement report may include received signal quality parameters suchas pilot signal strength (e.g., CPICH RSCP) for a serving macro cell,for a nearby femto cell, and for other nearby cells. As another example,a measurement report may indicate the total wideband received power on acarrier (e.g., Io or received signal strength indication (RSSI)). As yetanother example, a measurement report may include derived parameterssuch CPICH Ec/Io for a serving macro cell, for a nearby femto cell, andfor other nearby cells.

From these parameters and additional information such as the value ofthe access point's transmit power, estimates of quantities such as thepath loss from the access terminal to the access point may be obtained.Classically, these measurements reports have been used by the networkfor access terminal mobility (i.e., used to make handover decisions forthe access terminal).

As represented by block 206, instead of using this informationexclusively for mobility operations, the access point 108 sends reportmessages that include the measurement information for the non-servingaccess point 106 to the access point 106. For example, these reportmessages may comprise the measurement reports received at block 204 orthese report messages may simply include some of the measurement reportinformation from the measurements reports. The access point 108 may sendthe report messages to the access point 106 via the network entity 110or, in some cases, directly.

As an example of the case where message reports are sent via the networkentity 110 (e.g., representing a series of network entities), the accesspoint may send the report messages via the network backhaul whereby thenetwork entity 110 sends corresponding report messages to the accesspoint 106. In some cases, the access point 108 and/or the network entity110 may simply forward received measurement reports to the access point106. In other cases, as discussed in more detail below in conjunctionwith FIG. 5, the access point 108 and/or the network entity 110 mayprocess the received measurement report information in conjunction withsending the report messages to the access point 106. For example, theaccess point 108 and/or the network entity 110 may aggregate anyreceived messages and periodically send a group of messages to theaccess point 106.

As an example of the case where message reports are sent directly to theaccess point 106, some communication networks support non-backhaulsignaling connections between access points. For example, in a casewhere the access points 106 and 108 are both femto cells, the accesspoints 106 and 108 may be able to directly communicate with one another(e.g., via a femto (e.g., Home NodeB) management server).

As represented by block 208, the non-serving access point 106 receivesthe messages that include the measurement information that originated atthe access terminal 104. As discussed in more detail below inconjunction with FIG. 5, these messages may be received on an individualbasis (e.g., as each measurement report is generated) or on an aggregatebasis (e.g., groups of messages may be collected and sent periodicallyby a network entity).

As represented by block 210, the access point 106 (e.g., by operation ofa transmit power control component 112) controls transmit power of theaccess point 106 based on the received report messages. For example, asdiscussed in more detail below in conjunction with FIG. 3, in someimplementations the transmit power control component 112 employs anevent-based transmit power control algorithm whereby transmit power isadjusted based on the number of received report messages that areassociated with a particular event (e.g., messages that are triggered bythe occurrence of a specific event at the access terminal 104). Asanother example, as discussed in more detail below in conjunction withFIG. 4, in some implementations the transmit power control component 112employs a ranking-based transmit power control algorithm wherebytransmit power is adjusted based on a ranking of signal conditions atdifferent reporting access terminals.

Referring to FIG. 3, this flowchart describes an example of an eventcounting-based algorithm that may be employed at an access point tocontrol transmit power. Here, the events relate to measurement reportgeneration at non-served access terminals that are in the vicinity ofthe access point.

Typically, measurement report message generation at an access terminalis event triggered. For example, an access terminal may generate ameasurement report when the signal strength of an observed access pointexceeds a threshold. This threshold may take the form of, for example,an absolute value or a value relative to the best signal strengthobserved. One example of such an event is Event 1A defined in UMTS.

A large number of measurement reports corresponding to a particular typeof event by non-served access terminals may indicate leakage of accesspoint transmit power outside of the building (e.g., a femto cell user'shome) where the access point is deployed. Consequently, if the number ofmeasurement report triggering events that occur at non-served accessterminals is above a certain configurable threshold, the transmit powerof the access point and therefore the coverage range of the access pointis reduced to mitigate interference at these access terminals.Conversely, if the number of events is less than the same or some otherthreshold, the transmit power is increased to improve coverage forallowed access terminals (e.g., home access terminals).

Accordingly, as represented by block 302 of FIG. 3, at various points intime, an access point will receive measurement report-based messagesfrom one or more access terminals that are not currently being served bythe access point. For example, a femto cell may receive measurementreports generated by a nearby macro access terminal or by a nearbyaccess terminal that is being served by another femto cell. As discussedabove, a reporting access terminal may send measurements reports to itsserving access point after which the measurement report (or othersuitable message) is sent to the femto cell (e.g., via the backhaul orin some other manner).

As represented by block 304, the access point identifies the quantity ofreceived messages that indicate the occurrence of a specified type ofevent. Here, the quantity may be calculated over a defined period oftime (e.g., a day, a week, etc.).

For example, in an UMTS-based system, a femto cell may count the numberof a received measurement reports that were triggered by the occurrenceof Event 1A at the reporting access terminal(s). For example, an Event1A at a macro access terminal may correspond to the received signalpower from a femto cell being within a defined threshold (e.g., adefined dB amount) of the received signal power from the macro accessterminal's serving macro cell. In conjunction with such an event, themacro access terminal may attempt to add the femto cell to the macroaccess terminal's active set for handover-related operations.

As represented by block 306, the access point compares the quantitydetermined at block 304 to a threshold. It should be appreciated thatmore than one threshold may be employed in some cases. For example, onethreshold may be used to determine whether transmit power should bedecreased and another (e.g., lower) threshold may be used to determinewhether transmit power should be increased.

As represented by block 308, the access point controls its transmitpower based on the comparison of block 306. For example, the transmitpower may be decreased if the quantity is greater than (or greater thanor equal to) a threshold, while the transmit power may be increased ifthe quantity is less than (or less than or equal to) a threshold.

As a specific example, at defined update intervals, the access point mayupdate its transmit power level based on the formula: Pnew=Pcurrent+ΔP.In some implementations, the power adjustment ΔP is computed based onthe comparison of the quantity of measurement report events with athreshold.

As a specific example, the measurement reports corresponding to an eventof certain type (e.g., Event 1A) are counted during an update period.Let the number of these events be denoted by Observed_Event_Count. Thisquantity is then compared with a configurable threshold,Target_Event_Count, which controls the desired number of such events inthe update period. ΔP is then computed according to the formula:ΔP=g(Target_Event_Count−Observed_Event_Count). Here, g(x) may comprise amonotonic non-decreasing function which takes the value 0 for x=0 (i.e.,the transmit power is unchanged if the target is met).

In the above example, the direction of the transmit power adjustment(e.g., increase or decrease) as well as the magnitude of the transmitpower adjustment is based on the difference between the observed countand the target count. Accordingly, if the number of events issignificantly different than the target, a relatively large transmitpower adjustment may be made. Conversely, if the number of events isrelatively close to the target, a relatively small transmit poweradjustment may be made. In either case, the newly calculated transmitpower (Pnew) may be constrained by minimum and maximum transmit powerlimits (e.g., as specified for the access point and/or by anothertransmit power control algorithm).

Referring now to FIG. 4, this flowchart describes an example of ameasurement report content-based algorithm that may be employed at anaccess point to control transmit power. Here, the contents of receivedmeasurement reports are examined to obtain a subset of measurementreports that are useful for computation of the transmit power setting.Thus, in this case, the transmit power is determined not just based onthe number of measurement reports, but also based on the contents of themeasurement reports.

Such an algorithm may prove particularly advantageous, for example, inimplementations where the measurement reports consist of both eventtriggered reports and periodic reports. For example, event triggeredreports (e.g., based on Event 1A or some other event) may occur when amacro access terminal is at the boundary of femto cell coverage andmacro cell coverage. On the other hand, measurement reports underperiodic reporting may be generated anywhere within the femto cellcoverage. Consequently, periodic reporting may provide more detailedinformation regarding interference conditions in the vicinity of thefemto cell.

As represented by block 402 of FIG. 4, at various points in time, anaccess point may receive measurement report-based messages fromdifferent access terminals that are not currently being served by theaccess point. For example, a femto cell may receive measurements reportsoriginating from different macro access terminals that are passing bythe femto cell. In addition, the femto cell may receive measurementsreports originating from different access terminals that are served byother femto cells in the vicinity of the femto cell.

The received messages are grouped according to the originating accessterminal. For example, the messages originating from a first macroaccess terminal are placed in one group, the messages originating from asecond macro access terminal are placed in another group, the messagesoriginating from an access terminal being served by another femto cellare placed in yet another group, and so on.

The grouping of these messages may be performed at various entities inthe system. In some cases, the destination access point (e.g., the femtocell) for the messages performs the grouping. In some cases, a networkentity performs the grouping. For example, a network entity such as aradio network controller may aggregate all messages it receivesaccording to the originating access terminals. The network entity maythen send the grouped messages to the destination access point. In somecases, a serving access point (e.g., a macro cell or other femto cell)that receives measurement reports from originating access terminals maygroup these measurement reports according to the originating accessterminal.

As represented by block 404, the access terminals are ranked based onthe received messages. For example, based on information indicative ofsignal conditions (e.g., Ec/Io, CPICH RSCP) included in each group ofmessages, the access terminals may be ranked according to how the accessterminals are impacted by interference from the access point.

As a specific example, for each group of measurement reports, themeasurement reports indicating the worst impact of the femto cell on thecorresponding access terminal (e.g., macro access terminal) areselected. In other words, for each access terminal, the worst reportedsignal conditions are identified from that access terminal's measurementreport group.

The worst signal conditions (impact) may be determined in various ways.In some cases, the worst signal conditions are selected based on thelowest reported serving macro cell signal strength (e.g., CPICHRSCP_(macro) or CPICH Ec/Io_(macro)) when the reported femto cell signalstrength (e.g., CPICH RSCP_(femto) or CPICH Ec/Io_(femto)) is above acertain threshold. Thus, this determination provides an indication ofhow the transmissions by the femto cell are affecting reception of macrocell signals at the macro access terminal. In some cases, the worstsignal conditions are selected based on the highest reported femto cellsignal strength. This determination provides an indication of thestrength of the femto cell transmissions as seen by the macro accessterminal.

Once the worst signal conditions for each access terminal areidentified, the access terminals are ranked according to these signalsconditions. For example, the macro access terminal reporting the lowestmeasured macro cell signal strength may be given a rank of “1”, themacro access terminal reporting the next lowest macro cell signalstrength may be given a rank of “2”, and so on. As another example, themacro access terminal reporting the highest measured femto cell signalstrength may be given a rank of “1”, the macro access terminal reportingthe next highest femto cell signal strength may be given a rank of “2”,and so on.

As represented by block 406, a subset of the access terminals isdesignated based on the ranking of block 404. For example, a number ofthe access terminals associated with the worst signal conditions (e.g.,lowest macro cell signal strength or highest femto cell signal strength)may be “excluded,” leaving only the access terminals having the bettersignal conditions in the subset. Here, the number of access terminalsplaced in the subset may be determined based on a defined number ofaccess terminals or a defined portion (e.g., percentage) of thereporting access terminals. For example, the subset may be limited to 20access terminals or may be limited to 90% of the reporting accessterminals.

As a specific example, the size of the subset may be specified based ona configurable number, Target_Affected_UEs, that indicates a tolerablenumber of affected access terminals for a transmit power update period.For example, a femto cell may be configured so that it is allowed toaffect Target_Affected_UEs number of access terminals during a givenupdate period. In other words, it is deemed acceptable for theinterference caused by the femto cell at this number of macro accessterminals to exceed a defined level of interference (e.g., which maycorrespond to a level of interference that disrupts macro reception atthe macro access terminal). Hence, this quantity of the most affectedaccess terminals is “excluded” from the set of reporting accessterminals, thereby leaving a subset of access terminals for which thefemto cell's transmissions are not to cause interference. Accordingly,if the number of access terminals in the subset is greater than zero,the femto cell needs to ensure that its transmit power does not undulyinterfere with the access terminals in the subset.

As represented by block 408, the access point controls its transmitpower to achieve specified signal conditions at the subset of accessterminals. For example, the femto cell may adjust its transmit power, asnecessary, to cause an acceptable level of interference at the subset ofaccess terminals. In some cases, the transmit power may be adjusted sothat subsequently measured signal conditions (e.g., received macro cellsignal strength) corresponding to signals that the subset of accessterminals subsequently receive from the macro access point will begreater than or equal to a defined threshold. Conversely, in othercases, the transmit power may be adjusted so that subsequently measuredsignal conditions (e.g., received femto cell signal strength)corresponding to signals that the subset of access terminalssubsequently receive from the femto cell will be less than or equal to adefined threshold.

As a specific example, the transmit power of the femto cell iscalibrated so that the access terminal having the worst signalconditions of the subset of access terminals (e.g., the access terminalhaving the lowest number ranking in the subset) sees a macro signalstrength that is greater than or equal to a defined threshold. Here, thefemto cell may calculate this transmit power value since the femto cellmay determine the transmit power of the macro cell, the transmit powerof the femto cell, the path loss between the access terminal and themacro cell, and the path loss between the access terminal and the femtocell.

As above, the newly calculated transmit power (Pnew) may be constrainedby minimum and maximum transmit power limits (e.g., as specified for theaccess point and/or by another transmit power control algorithm).

FIG. 5 describes sample operations that may be performed at a networkentity to handle measurement report-related messaging in conjunctionwith the transmit power control techniques described herein. Asdiscussed herein, the network entity may take various forms including,for example, a radio network controller, a femto management server, oran access point (e.g., a macro access point or a femto access point).

As represented by block 502, at various points in time, the networkentity receives measurement reports that originate from one or moreaccess terminals. For example, a core network entity (e.g., a radionetwork controller) may receive measurement report-related messages fromdifferent access points managed by that network entity. As anotherexample, an access point may receive measurement reports from variousaccess terminals served by that access point.

As discussed herein, the measurement reports generated by a given accessterminal typically include measurement information for several accesspoints. Thus, a network entity will receive measurement reports directedto different access points. Accordingly, to facilitate transmit powercalibration at a specific access point in accordance with the teachingsherein, the network entity identifies those measurement reportscorresponding to the specified (i.e., the same) access point.

As represented by block 504, the network entity determines whether thespecified access point controls transmit power based on measurementreports. For example, if the access point does not control transmitpower in this manner, the network entity may simply use the measurementreports for conventional handover-related operations rather thantransmit power calibration (e.g., interference management). Conversely,if the network entity determines that the access point does controltransmit power based on measurement reports from non-served accessterminals, the network entity takes appropriate action to send thisinformation to the access point.

As represented by block 506, as discussed herein, the network entity mayaggregate received measurement reports based on which access terminalsent a given measurement report. That is, the network entity may groupall of the measurement reports from a given access terminal together.

As represented by block 508, the access point sends the measurementreports to the specified access point as a result of the determination(at block 504) that the access point controls transmit power based onmeasurement reports. The measurement reports may be sent in differentways in different implementations. In some cases, the network entitysimply sends the measurement reports upon receipt (e.g., the networkentity does not aggregate the measurement reports or schedule theirdelivery at pre-designated times). In other cases, the network entityaggregates the measurement reports (e.g., as discussed herein) and sendsthe measurement reports in corresponding groups. In these cases, eachmeasurement report group may be sent along with an indication thatidentifies the access terminal from which the measurement reportsoriginated. Also, in some cases (e.g., in the case of aggregation), thenetwork entity schedules the sending of the measurement report-basedmessages. For example, the messages may be sent periodically, once everytransmit power update period.

The sending of the measurement reports may be initiated in various ways.In some cases, the network entity sends the measurement reports on aperiodic basis. In some cases, the sending of the measurement reports bythe network entity is triggered by a request from the specified accesspoint.

The network entity may uniquely identify the destination access pointfor the measurement report messages in various ways. In someimplementations access terminals include a unique identifier (e.g., acell identifier) of the access point in the measurement report. Forexample, the access terminal may acquire this identifier from abroadcast signal transmitted by the access point. In someimplementations, the unique identity of an access point is determinedbased on different timing information used by different access points ina network. Other access point identity disambiguation techniques may beemployed in other cases.

Referring now to the system 600 of FIG. 6, in some implementations theabove-described measurement report transmit power schemes may beemployed in a multi-stage transmit power control scheme. For example,the access point 606 may jointly employ network listen-based powercalibration (NLPC) functionality as represented by the block 612, mobileassisted range tuning (MART) functionality as represented by the block614, and active mobile protection functionality as represented by theblock 616. At any given point in time, transmit power is controlled(e.g., calibrated) depending on the state of the access point 606.

In a sample implementation, these states may comprise an initialization(e.g., power-up or recalibration) state, a post-initialization state,and a state relating to the detection of the presence of an active macrouser in the vicinity of the access point 606. For example, when theaccess point 606 is powered-up, the access point 606 initially usesNLPC.

Subsequently, the access point 606 uses mobile (i.e., access terminal)assisted range tuning For example, the access point 606 may switch tothe MART state after it collects a sufficient amount of information fromnearby access terminals. This information may be collected in differentways and may take different forms. For example, at various points intime, the access point 606 will transmit information on its servicechannel and may also transmit on one or more beacon channels. As aresult of these transmissions, the access point 606 may receive messagesfrom nearby access terminals.

In some cases, MART is based on measurement report messages generated bya nearby access terminal (e.g., the access terminal 604) that is notcurrently being served by the access point 606. Here, the accessterminal 604 may send measurement report messages to its serving accesspoint (e.g., the access point 608), after which the messages areforwarded to the non-serving access point 606 (e.g., via the backhaul)and used for power control as described above at FIGS. 1-4.

In some cases, MART is based on measurement report messages generated bya nearby access terminal (e.g., the access terminal 602) that isauthorized to obtain active mode service via the access point 606. Inthis case, the access terminal 602 sends the measurement report messagesdirectly to the access point 606. These measurement report messages mayreport the channel quality (e.g., in terms of signal power) measured atthe access terminal 602 for the femto forward link service channeland/or the beacon channel(s). In some cases, the access point 606 mayrequest the access terminal to measure channel quality on the femtoservice channel and/or the beacon channel(s) and report this informationback using measurement report messages. Additionally, in some cases, theaccess point 606 may request the access terminal to report path loss onthe femto service channel and/or the beacon channel and report thisinformation back using measurement report messages.

In some cases, MART is based on registration messages received from anearby access terminal (e.g., the access terminal 604) that is notauthorized to receive active mode service from the access point 606.Here, the access terminal 604 may be served by another access point(e.g., the access point 608) or may be in idle mode. The access terminal604 may attempt to register with the access point 606 as a result ofreceiving forward link signals, pilots, or beacons from the access point606. Consequently, the access terminal 604 will send registrationmessages to the access point 606. However, since the access terminal isnot allowed to access active mode service via the access point 606, thisregistration request will fail. As discussed in more detail below, as aresult of receiving these registration messages, the access point 606may determine how to best adjust its transmit power to provide anacceptable tradeoff between providing adequate coverage and minimizinginterference to such non-allowed access terminals. In some cases, theaccess point 606 may request that one or more of signal power, qualityor path loss to be reported as a part of a registration message from theaccess terminal 604.

In the MART state, the access point 606 may continually (e.g.,periodically) update the transmit power. For example, the access point606 may acquire information from nearby access terminals (e.g., channelquality, received power, and path loss reports from non-served accessterminal and/or home access terminal, and registration statistics) andthen fine tune the transmit power on a periodic basis (e.g., accordingto the update period discussed above) based on this information.

In addition, while in the MART state, the access point 606 may regularlymonitor network conditions to determine whether there has been asignificant change in network conditions (e.g., due to a change in femtocell location and/or installation/removal of access points in thevicinity). If so, the access point 606 may switch back to the networklisten-based power calibration state to update one or more power controlparameters (e.g., transmit power limits). For example, a femto cell mayperiodically perform network listen measurements and performsrecalibration if the RF environment has changed. A change in the RFenvironment may be detected (e.g., a change in channel conditionsidentified) by comparing previous network listen measurements (e.g.,previously received pilot signals) with the new network listenmeasurements (e.g., newly received pilot signals). If a change isdetected, transmit power may be re-calibrated (e.g., by setting at leastone transmit power limit based on the identified channel conditions). Insome cases, this may involve combining network listen measurements withpreviously learned information from received messages. The periodicityof making network listen measurements for recalibration may be smallerthan the MART periodicity. Also, recalibration is done under events suchas when the access points is re-powered up, when the RF environment haschanged, or when the access point is explicitly directed to re-calibrateby the network.

Also, while in the NLPC state or the MART state, the access point 606may regularly (e.g., continually) monitor for the presence of any nearbyactive users. For example, a femto cell may periodically switch to anactive mobile protection (AMP) state to monitor for nearby active macrousers by measuring out-of-cell interference on one or more reverse linkfrequencies. In the event a nearby active user is detected on a givencarrier frequency, the access point 606 switches to the active mobileprotection state. Here, the access point 606 may temporarily limit itstransmissions by, for example, reducing transmit power or ceasingtransmission on that carrier frequency. Then, upon determining that theuser is no longer nearby or is no longer active, the access point 606returns to the previous state (e.g., NLPC or MART).

From the above, it should be appreciated that while in the NLPC state,the access point 606 may transmit using transmit power parametersdetermined by an NLPC algorithm. Conversely, while in the MART state,the access point 606 may transmit using transmit power parametersdetermined by one or more MART algorithms, whereby the transmit powerparameters are determined based on messages received from at least oneaccess terminal (e.g., a home access terminal and/or an alien accessterminal). In the MART state, the access point 606 will continuecollecting messages from the at least access terminal. In addition, foractive mobile protection, the access point 606 may regularly monitor forother access terminals (e.g., active macro access terminals) that may besubject to interference from the access point 606.

The transmit power schemes (e.g., NLPC, MART, AMP) may interact indifferent ways in different implementations. In some cases, differenttransmit power schemes may be used in succession to control transmitpower during different states. For example, as discussed above, NLPC maybe employed at initialization. NLPC may then be superseded by MARTwhich, in turn, is occasionally superseded by AMP. In other cases, onetransmit power scheme may provide one or more parameters used by anotherscheme. For example, NLPC may be used to provide a set of minimum andmaximum transmit power limits that are subsequently used by a non-servedaccess terminal measurement report-based MART algorithm or aregistration message-based MART algorithm. As another example, a homeaccess terminal (HAT) report-based MART algorithm may be used to providea set of minimum and maximum transmit power limits that are subsequentlyused by a non-served access terminal measurement report-based MARTalgorithm or a registration message-based MART algorithm.

FIG. 7 illustrates sample operations that may be performed onconjunction with a multi-state transmit power control scheme. Asindicated in the flowchart, one or more of NLPC, AMP, HAT report-basedMART, or registration message-based MART may optionally be employed in agiven implementation in conjunction with the non-served access terminalreport-bases algorithms taught herein.

As represented by block 702, an access point (e.g., a femto cell) may bepowered-up, reset, or subjected to some other procedure that commencesinitialization of the access point. The access point then employsnetwork listen-based power calibration (NLPC) after initialization iscommenced. In some aspects, this involves monitoring one or morechannels (e.g., on a corresponding carrier frequency) to determine thecorresponding channel quality (e.g., received signal strength) as seenby the access point. An access point may perform this monitoring using anetwork listen module (NLM) or other suitable component(s). Based on thedetermined channel quality, the access point sets the initial transmitpower to be used by the access point. This initial transmit power maycomprise, for example, an initial value to be used for the transmitpower or an initial range (e.g., specified by minimum and maximumlimits) within which the transmit power is to be limited.

In so-called co-channel deployments, a femto cell is deployed on thesame carrier frequency as a macro cell. That is, the femto cell'sforward link (also referred to as the downlink) is on the same carrierfrequency as the macro cell's forward link. In this case, the femto cellmay use NLPC to control transmit power on this carrier frequency tomitigate any interference the femto cell's transmissions may have onnearby access terminals (e.g., macro access terminals) operating on thisfrequency.

Here, the femto cell's forward link transmit power may be calibrated bymeasuring the surrounding macro cells' forward link channel quality(e.g., RSSI, CPICH Ec/Io, RSCP). The femto cell uses the macro cell RSSImeasurements and a defined coverage radius (as an input) to set theinitial transmit power. The transmit power is chosen to satisfy an idlereselection requirement. For example, the femto cell CPICH Ec/Io shouldbe better than Qqualmin for the femto cell at the edge of the coverageradius (or at a given path loss). To achieve this, the transmit powerlevel is chosen as a function of the measured macro quality (CPICH/Io)and a path loss value. Furthermore, to limit interference induced atnearby access terminals (e.g., macro access terminals), anotherpotential requirement is for the femto cell transmission to increase Ioby at most a certain fixed amount at the edge of the femto cell coveragerange (or at a given path loss). The femto cell transmit power is thenchosen to be the minimum of these two criteria. Again, this allows thefemto cell to adapt its transmit power based on its location in themacro network. The transmit power is set lower at a location where macrocell RSSI is weak as compared to a location where macro cell RSSI isstrong.

As represented by block 704, an access point also may employ activemobile protection in some implementations. For example, a femto cell'sforward link transmissions may degrade the voice call quality of activemacro users in the vicinity of the femto cell. To protect these activemacro mobiles from such interference, whenever the presence of a nearbyactive macro user is detected, the femto cell temporarily throttles(i.e., restricts) its forward link transmissions.

Accordingly, an access point may regularly (e.g., continuously) monitorfor the presence of nearby active non-home access terminals (e.g.,active macro access terminals) and take action to restrict the accesspoint's transmissions until that access terminal leaves the vicinity orends the active communication. Once there are no longer any such activeaccess terminals in the vicinity of the access point, the access pointmay resume using the transmit power level dictated by the other transmitpower algorithms (e.g., NLPC or MART).

An access point may restrict its transmission in various ways. Forexample, the access point may temporarily reduce its transmit power,temporarily reduce the periodicity of its transmissions, or temporarilycease transmission. The access point may restrict its transmission for adefined period of time or the access point may restrict its transmissionuntil a terminating event occurs. For example, in cases where detectionof an access terminal is based on a measured received signal strengthexceeding a threshold, the access point may terminate the restriction oftransmission when measured received signal strength falls below acertain configurable threshold. In any of these cases, upon terminatingthe restriction of transmission, the access point may resumetransmitting at the transmit power level and/or periodicity that wasused prior to the restriction of transmission.

An access point may detect the presence of an active access terminal invarious ways. In some implementations, the femto cell detects thepresence of a nearby macro cell user by measuring received signalstrength on the macro cell reverse link carrier frequency that is (orfrequencies that are) paired with a macro cell forward link carrierfrequency (or frequencies). For example, the measurement of a reverselink RSSI value that exceeds a certain expected value (e.g., athreshold) over a period of time may serve as an indication of thepresence of an active macro cell user that is receiving on thecorresponding forward link frequency. In some implementations, thepresence of a nearby active macro cell user may be known apriori to theaccess point. For example, in a case of active handover of an accessterminal from a femto cell to a macro cell (commonly referred to asactive hand-out) for a restricted user or guest user, the femto cellwill know that this access terminal is in the vicinity of the femto celland is now being served by the macro cell.

As represented by block 706, an access point may regularly (e.g.,periodically) monitor for changes in channel quality to determinewhether to temporarily revert back to NLPC. For example, if there hasbeen a recent significant change in channel quality (e.g., due to achange in the location of the access point, and/or installation/removalof access points in the vicinity), the information collected for MARTmay be considered unreliable. In such a case, the access point mayswitch back to the NLPC state to reestablish initial transmit powerlimits for the access point until new MART information is acquired.

Thus, in addition to initial power setting upon initialization, the NLPCtechnique may be used for recalibration purposes to identify changes inthe RF environment due to events such as a change in an access point'slocation and adjust the transmit power accordingly. Such recalibrationmay be initiated autonomously by the access point or directed by thenetwork. Recalibration may also be initiated upon re-power-up or resetof the femto cell. After reset or re-power-up, the femto cell may firstcheck for changes in channel quality. If no significant change isdetected, the femto cell may use the transmit power that was used priorto the reset or re-power-up event. Otherwise, the femto cell may switchback to the NLPC state to reestablish initial transmit power levels.

As discussed above, NLPC has certain inherent limitations. Consequentlyas represented by block 708, MART may be used to periodically adjust theaccess point's transmit power. For example, after applying NLPC, MARTmay be performed regularly (e.g., every 24 hours, every couple of days,etc.) based on messages received at the access point as discussedherein. In this way, MART may be used to determine optimal long termtransmit power levels for the access point.

As represented by block 710, in some implementations, MART is based onchannel quality reports sent by home access terminals (HAT reports). Insome aspects, adequate coverage for home access terminals may be ensuredthrough the use of HAT reports. Based on HAT feedback, a femto cell maylearn the desired coverage range (i.e., path loss at different locationsin the building) and RF conditions in the building and then choose anoptimal transmit power level. For example, a femto cell may transmit ata relatively higher power when deployed in a large building as comparedto when deployed in a small building. In some implementations, a changein transmit power based on HAT reports may not be made until the accesspoint has received a sufficient number (e.g., a defined number) of HATreports.

As represented by block 712, in some implementations, MART is based onstatistics of registrations performed by access terminals (e.g.,preferred access terminals or non-home access terminals such as macroaccess terminals) that are in the femto cell's coverage. Theregistration statistics may correspond to, for example, the number ofregistrations attempts (e.g., failed registrations by alien accessterminals) made at the access point over a defined period of time. Insome aspects, a large number of registrations by alien access terminalsis an indication of leakage outside the home. Therefore, when the numberof registrations by alien access terminals is above a certainconfigurable threshold, transmit power and therefore the coverage rangeof the femto cell is reduced to control interference to alien accessterminals.

As represented by block 714, in accordance with the teachings herein,MART may be based on measurement report messages received fromnon-served access terminals as discussed above at FIGS. 1-4.

As represented by block 716, the access point sets its transmit powerbased on the messages collected at one or more of blocks 710-714. Byusing information from these messages, the femto cell may choose adesired transmit power setting to balance the coverage versusinterference minimization trade-off. For example, using received HATreports, a femto cell may estimate the path loss to a home accessterminal at different locations in a building as well as the macrochannel quality (and/or received signal power) at these locations. Thefemto cell may thus learn the required coverage range and RF conditionsin the building and fine tune its transmit power accordingly. As aresult, the femto cell may automatically transmit at a relatively higherpower when deployed in a large building as compared to when it isdeployed in a small building.

As a restriction on this transmit power determination, however, thefemto cell may use registration statistics and/or non-served measurementreports to mitigate interference to nearby non-served access terminals.For example, the transmit power may be scaled back from the HATreport-based transmit power value based on whether: a large number ofregistration messages are received, a large number of event triggeredmeasurement reports are received, more than the tolerable number ofaccess terminals are subjected to interference, or based on somecombination of these factors.

The transmit power control schemes described herein may be implementedin a variety of ways in different implementations. For example, theteachings herein may be employed to control transmit power on varioustypes of channels.

In addition, an access point may acquire measurement report informationin various ways. For example, in some implementations an access pointmay acquire this information by monitoring the forward link of nearbyaccess terminals.

FIG. 8 illustrates several sample components (represented bycorresponding blocks) that may be incorporated into nodes such as anaccess point 802 (e.g., corresponding to the access point 106 or theaccess point 606) and a network entity 804 (e.g., corresponding to thenetwork entity 110 or an access point as discussed above) to performtransmit power control-related operations as taught herein. Thedescribed components also may be incorporated into other nodes in acommunication system. For example, other nodes in a system may includecomponents similar to those described for the access point 802 and thenetwork entity 804 to provide similar functionality. Also, a given nodemay contain one or more of the described components. For example, anaccess point may contain multiple transceiver components that enable theaccess point to operate on multiple carriers and/or communicate viadifferent technologies.

As shown in FIG. 8, the access point 802 includes a transceiver 806 forcommunicating with other nodes. The transceiver 806 includes atransmitter 808 for sending signals (e.g., data, beacons, messages) onone or more carrier frequencies and a receiver 810 for receiving signals(e.g., messages, registration messages, pilot signals, measurementreports) on one or more carrier frequencies. In implementations wherethe network entity 804 supports wireless communication (e.g., where thenetwork entity comprises an access point), the network entity 804 alsoincludes a transceiver 812 comprising a transmitter 814 and a receiver816 for communicating with other nodes.

The access point 802 and the network entity 804 also include networkinterfaces 818 and 820, respectively, for communicating with other nodes(e.g., network entities). For example, the network interfaces 818 and820 may be configured to communicate with one or more network entitiesvia a wire-based or wireless backhaul. In some aspects, the networkinterfaces 818 and 820 may be implemented as a transceiver (e.g.,including transmitter and receiver components) configured to supportwire-based or wireless communication. Accordingly, in the example ofFIG. 8, the network interface 818 is shown as including a transmitter822 and a receiver 824 for sending and receiving messages (e.g.,measurement reports), while the network interface 820 is shown asincluding a transmitter 826 and a receiver 828 for sending and receivingmessages (e.g., measurement reports).

The access point 802 and the network entity 804 include other componentsthat may be used in conjunction with transmit control-related operationsas taught herein. For example, the access point 802 includes a transmitpower controller 830 for controlling transmit power of the access point802 (e.g., identifying a quantity of messages, comparing the quantity toa threshold, controlling transmit power based on the comparison,determining that an access terminal is actively receiving information,restricting transmission, identifying channel conditions, setting atleast one limit for transmit power, ranking access terminals,designating a subset of the access terminals, controlling transmit powerto achieve specified signal conditions at the subset of accessterminals) and for providing other related functionality as taughtherein. In some implementations, some of the functionality of thetransmit power controller 830 may be implemented in the receiver 810and/or the transmitter 808. The network entity 804 includes ameasurement report controller 832 for handling measurementreport-related messaging (e.g., determining that an access pointcontrols transmit power based on measurement reports, aggregatingmeasurement reports) and for providing other related functionality astaught herein. The access point 802 and the network entity 804 also mayinclude communication controllers 834 and 836, respectively, forcontrolling communications (e.g., sending and receiving messages) andfor providing other related functionality as taught herein. Also, theaccess point 802 and the network entity 804 include memory components838 and 840 (e.g., each including a memory device), respectively, formaintaining information (e.g., received message information).

For convenience, the access point 802 and the network entity 804 areshown in FIG. 8 as including components that may be used in the variousexamples described herein. In practice, the functionality of one or moreof these blocks may be different in different embodiments. For example,the functionality of block 830 may be different in a deploymentimplemented according to FIG. 3 as compared to a deployment implementedaccording to FIG. 4.

The components of FIG. 8 may be implemented in various ways. In someimplementations the components of FIG. 8 may be implemented in one ormore circuits such as, for example, one or more processors and/or one ormore ASICs (which may include one or more processors). Here, eachcircuit (e.g., processor) may use and/or incorporate data memory forstoring information or executable code used by the circuit to providethis functionality. For example, some of the functionality representedby blocks 806 and 818, and some or all of the functionality representedby blocks 830, 834, and 838 may be implemented by a processor orprocessors of an access point and data memory of the access point (e.g.,by execution of appropriate code and/or by appropriate configuration ofprocessor components). Similarly, some of the functionality representedby blocks 812 and 820, and some or all of the functionality representedby blocks 832, 836, and 840 may be implemented by a processor orprocessors of a network entity and data memory of the network entity(e.g., by execution of appropriate code and/or by appropriateconfiguration of processor components).

As discussed above, in some aspects the teachings herein may be employedin a network that includes macro scale coverage (e.g., a large areacellular network such as a 3G network, typically referred to as a macrocell network or a WAN) and smaller scale coverage (e.g., aresidence-based or building-based network environment, typicallyreferred to as a LAN). As an access terminal (AT) moves through such anetwork, the access terminal may be served in certain locations byaccess points that provide macro coverage while the access terminal maybe served at other locations by access points that provide smaller scalecoverage. In some aspects, the smaller coverage nodes may be used toprovide incremental capacity growth, in-building coverage, and differentservices (e.g., for a more robust user experience).

In the description herein, a node (e.g., an access point) that providescoverage over a relatively large area may be referred to as a macroaccess point while a node that provides coverage over a relatively smallarea (e.g., a residence) may be referred to as a femto access point. Itshould be appreciated that the teachings herein may be applicable tonodes associated with other types of coverage areas. For example, a picoaccess point may provide coverage (e.g., coverage within a commercialbuilding) over an area that is smaller than a macro area and larger thana femto area. In various applications, other terminology may be used toreference a macro access point, a femto access point, or other accesspoint-type nodes. For example, a macro access point may be configured orreferred to as an access node, base station, access point, eNodeB, macrocell, and so on. Also, a femto access point may be configured orreferred to as a Home NodeB, Home eNodeB, access point base station,femto cell, and so on. In some implementations, a node may be associatedwith (e.g., referred to as or divided into) one or more cells orsectors. A cell or sector associated with a macro access point, a femtoaccess point, or a pico access point may be referred to as a macro cell,a femto cell, or a pico cell, respectively.

FIG. 9 illustrates a wireless communication system 900, configured tosupport a number of users, in which the teachings herein may beimplemented. The system 900 provides communication for multiple cells902, such as, for example, macro cells 902A-902G, with each cell beingserviced by a corresponding access point 904 (e.g., access points904A-904G). As shown in FIG. 9, access terminals 906 (e.g., accessterminals 906A-906L) may be dispersed at various locations throughoutthe system over time. Each access terminal 906 may communicate with oneor more access points 904 on a forward link (FL) and/or a reverse link(RL) at a given moment, depending upon whether the access terminal 906is active and whether it is in soft handoff, for example. The wirelesscommunication system 900 may provide service over a large geographicregion. For example, macro cells 902A-902G may cover a few blocks in aneighborhood or several miles in a rural environment.

FIG. 10 illustrates an exemplary communication system 1000 where one ormore femto access points are deployed within a network environment.Specifically, the system 1000 includes multiple femto access points 1010(e.g., femto access points 1010A and 1010B) installed in a relativelysmall scale network environment (e.g., in one or more user residences1030). Each femto access point 1010 may be coupled to a wide areanetwork 1040 (e.g., the Internet) and a mobile operator core network1050 via a DSL router, a cable modem, a wireless link, or otherconnectivity means (not shown). As will be discussed below, each femtoaccess point 1010 may be configured to serve associated access terminals1020 (e.g., access terminal 1020A) and, optionally, other (e.g., hybridor alien) access terminals 1020 (e.g., access terminal 1020B). In otherwords, access to femto access points 1010 may be restricted whereby agiven access terminal 1020 may be served by a set of designated (e.g.,home) femto access point(s) 1010 but may not be served by anynon-designated femto access points 1010 (e.g., a neighbor's femto accesspoint 1010).

FIG. 11 illustrates an example of a coverage map 1100 where severaltracking areas 1102 (or routing areas or location areas) are defined,each of which includes several macro coverage areas 1104. Here, areas ofcoverage associated with tracking areas 1102A, 1102B, and 1102C aredelineated by the wide lines and the macro coverage areas 1104 arerepresented by the larger hexagons. The tracking areas 1102 also includefemto coverage areas 1106. In this example, each of the femto coverageareas 1106 (e.g., femto coverage areas 1106B and 1106C) is depictedwithin one or more macro coverage areas 1104 (e.g., macro coverage areas1104A and 1104B). It should be appreciated, however, that some or all ofa femto coverage area 1106 may not lie within a macro coverage area1104. In practice, a large number of femto coverage areas 1106 (e.g.,femto coverage areas 1106A and 1106D) may be defined within a giventracking area 1102 or macro coverage area 1104. Also, one or more picocoverage areas (not shown) may be defined within a given tracking area1102 or macro coverage area 1104.

Referring again to FIG. 10, the owner of a femto access point 1010 maysubscribe to mobile service, such as, for example, 3G mobile service,offered through the mobile operator core network 1050. In addition, anaccess terminal 1020 may be capable of operating both in macroenvironments and in smaller scale (e.g., residential) networkenvironments. In other words, depending on the current location of theaccess terminal 1020, the access terminal 1020 may be served by a macrocell access point 1060 associated with the mobile operator core network1050 or by any one of a set of femto access points 1010 (e.g., the femtoaccess points 1010A and 1010B that reside within a corresponding userresidence 1030). For example, when a subscriber is outside his home, heis served by a standard macro access point (e.g., access point 1060) andwhen the subscriber is at home, he is served by a femto access point(e.g., access point 1010A). Here, a femto access point 1010 may bebackward compatible with legacy access terminals 1020.

A femto access point 1010 may be deployed on a single frequency or, inthe alternative, on multiple frequencies. Depending on the particularconfiguration, the single frequency or one or more of the multiplefrequencies may overlap with one or more frequencies used by a macroaccess point (e.g., access point 1060).

In some aspects, an access terminal 1020 may be configured to connect toa preferred femto access point (e.g., the home femto access point of theaccess terminal 1020) whenever such connectivity is possible. Forexample, whenever the access terminal 1020A is within the user'sresidence 1030, it may be desired that the access terminal 1020Acommunicate only with the home femto access point 1010A or 1010B.

In some aspects, if the access terminal 1020 operates within the macrocellular network 1050 but is not residing on its most preferred network(e.g., as defined in a preferred roaming list), the access terminal 1020may continue to search for the most preferred network (e.g., thepreferred femto access point 1010) using a better system reselection(BSR) procedure, which may involve a periodic scanning of availablesystems to determine whether better systems are currently available andsubsequently acquire such preferred systems. The access terminal 1020may limit the search for specific band and channel. For example, one ormore femto channels may be defined whereby all femto access points (orall restricted femto access points) in a region operate on the femtochannel(s). The search for the most preferred system may be repeatedperiodically. Upon discovery of a preferred femto access point 1010, theaccess terminal 1020 selects the femto access point 1010 and registerson it for use when within its coverage area.

Access to a femto access point may be restricted in some aspects. Forexample, a given femto access point may only provide certain services tocertain access terminals. In deployments with so-called restricted (orclosed) access, a given access terminal may only be served by the macrocell mobile network and a defined set of femto access points (e.g., thefemto access points 1010 that reside within the corresponding userresidence 1030). In some implementations, an access point may berestricted to not provide, for at least one node (e.g., accessterminal), at least one of: signaling, data access, registration,paging, or service.

In some aspects, a restricted femto access point (which may also bereferred to as a Closed Subscriber Group Home NodeB) is one thatprovides service to a restricted provisioned set of access terminals.This set may be temporarily or permanently extended as necessary. Insome aspects, a Closed Subscriber Group (CSG) may be defined as the setof access points (e.g., femto access points) that share a common accesscontrol list of access terminals.

Various relationships may thus exist between a given femto access pointand a given access terminal. For example, from the perspective of anaccess terminal, an open femto access point may refer to a femto accesspoint with unrestricted access (e.g., the femto access point allowsaccess to any access terminal). A restricted femto access point mayrefer to a femto access point that is restricted in some manner (e.g.,restricted for access and/or registration). A home femto access pointmay refer to a femto access point on which the access terminal isauthorized to access and operate on (e.g., permanent access is providedfor a defined set of one or more access terminals). A hybrid (or guest)femto access point may refer to a femto access point on which differentaccess terminals are provided different levels of service (e.g., someaccess terminals may be allowed partial and/or temporary access whileother access terminals may be allowed full access). An alien femtoaccess point may refer to a femto access point on which the accessterminal is not authorized to access or operate on, except for perhapsemergency situations (e.g., 911 calls).

From a restricted femto access point perspective, a home access terminalmay refer to an access terminal that is authorized to access therestricted femto access point installed in the residence of that accessterminal's owner (usually the home access terminal has permanent accessto that femto access point). A guest access terminal may refer to anaccess terminal with temporary access to the restricted femto accesspoint (e.g., limited based on deadline, time of use, bytes, connectioncount, or some other criterion or criteria). An alien access terminalmay refer to an access terminal that does not have permission to accessthe restricted femto access point, except for perhaps emergencysituations, for example, such as 911 calls (e.g., an access terminalthat does not have the credentials or permission to register with therestricted femto access point).

For convenience, the disclosure herein describes various functionalityin the context of a femto access point. It should be appreciated,however, that a pico access point may provide the same or similarfunctionality for a larger coverage area. For example, a pico accesspoint may be restricted, a home pico access point may be defined for agiven access terminal, and so on.

The teachings herein may be employed in a wireless multiple-accesscommunication system that simultaneously supports communication formultiple wireless access terminals. Here, each terminal may communicatewith one or more access points via transmissions on the forward andreverse links. The forward link (or downlink) refers to thecommunication link from the access points to the terminals, and thereverse link (or uplink) refers to the communication link from theterminals to the access points. This communication link may beestablished via a single-in-single-out system, amultiple-in-multiple-out (MIMO) system, or some other type of system.

A MIMO system employs multiple (N_(T)) transmit antennas and multiple(N_(R)) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, which are also referred to as spatialchannels, where N_(S)≦min{N_(T), N_(R)}. Each of the N_(S) independentchannels corresponds to a dimension. The MIMO system may provideimproved performance (e.g., higher throughput and/or greaterreliability) if the additional dimensionalities created by the multipletransmit and receive antennas are utilized.

A MIMO system may support time division duplex (TDD) and frequencydivision duplex (FDD). In a TDD system, the forward and reverse linktransmissions are on the same frequency region so that the reciprocityprinciple allows the estimation of the forward link channel from thereverse link channel. This enables the access point to extract transmitbeam-forming gain on the forward link when multiple antennas areavailable at the access point.

FIG. 12 illustrates a wireless device 1210 (e.g., an access point) and awireless device 1250 (e.g., an access terminal) of a sample MIMO system1200. At the device 1210, traffic data for a number of data streams isprovided from a data source 1212 to a transmit (TX) data processor 1214.Each data stream may then be transmitted over a respective transmitantenna.

The TX data processor 1214 formats, codes, and interleaves the trafficdata for each data stream based on a particular coding scheme selectedfor that data stream to provide coded data. The coded data for each datastream may be multiplexed with pilot data using OFDM techniques. Thepilot data is typically a known data pattern that is processed in aknown manner and may be used at the receiver system to estimate thechannel response. The multiplexed pilot and coded data for each datastream is then modulated (i.e., symbol mapped) based on a particularmodulation scheme (e.g., BPSK, QSPK, M-PSK, or M-QAM) selected for thatdata stream to provide modulation symbols. The data rate, coding, andmodulation for each data stream may be determined by instructionsperformed by a processor 1230. A data memory 1232 may store programcode, data, and other information used by the processor 1230 or othercomponents of the device 1210.

The modulation symbols for all data streams are then provided to a TXMIMO processor 1220, which may further process the modulation symbols(e.g., for OFDM). The TX MIMO processor 1220 then provides N_(T)modulation symbol streams to N_(T) transceivers (XCVR) 1222A through1222T. In some aspects, the TX MIMO processor 1220 applies beam-formingweights to the symbols of the data streams and to the antenna from whichthe symbol is being transmitted.

Each transceiver 1222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transceivers 1222A through 1222T are thentransmitted from N_(T) antennas 1224A through 1224T, respectively.

At the device 1250, the transmitted modulated signals are received byN_(R) antennas 1252A through 1252R and the received signal from eachantenna 1252 is provided to a respective transceiver (XCVR) 1254Athrough 1254R. Each transceiver 1254 conditions (e.g., filters,amplifies, and downconverts) a respective received signal, digitizes theconditioned signal to provide samples, and further processes the samplesto provide a corresponding “received” symbol stream.

A receive (RX) data processor 1260 then receives and processes the N_(R)received symbol streams from N_(R) transceivers 1254 based on aparticular receiver processing technique to provide N_(T) “detected”symbol streams. The RX data processor 1260 then demodulates,deinterleaves, and decodes each detected symbol stream to recover thetraffic data for the data stream. The processing by the RX dataprocessor 1260 is complementary to that performed by the TX MIMOprocessor 1220 and the TX data processor 1214 at the device 1210.

A processor 1270 periodically determines which pre-coding matrix to use(discussed below). The processor 1270 formulates a reverse link messagecomprising a matrix index portion and a rank value portion. A datamemory 1272 may store program code, data, and other information used bythe processor 1270 or other components of the device 1250.

The reverse link message may comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message is then processed by a TX data processor 1238,which also receives traffic data for a number of data streams from adata source 1236, modulated by a modulator 1280, conditioned by thetransceivers 1254A through 1254R, and transmitted back to the device1210.

At the device 1210, the modulated signals from the device 1250 arereceived by the antennas 1224, conditioned by the transceivers 1222,demodulated by a demodulator (DEMOD) 1240, and processed by a RX dataprocessor 1242 to extract the reverse link message transmitted by thedevice 1250. The processor 1230 then determines which pre-coding matrixto use for determining the beam-forming weights then processes theextracted message.

FIG. 12 also illustrates that the communication components may includeone or more components that perform transmit power control operations astaught herein. For example, a transmit power control component 1290 maycooperate with the processor 1230 and/or other components of the device1210 to control transmit power for transmissions by the device 1210(e.g., transmissions to another device such as the device 1250) astaught herein. It should be appreciated that for each device 1210 and1250 the functionality of two or more of the described components may beprovided by a single component. For example, a single processingcomponent may provide the functionality of the transmit power controlcomponent 1290 and the processor 1230.

The teachings herein may be incorporated into various types ofcommunication systems and/or system components. In some aspects, theteachings herein may be employed in a multiple-access system capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., by specifying one or more of bandwidth, transmitpower, coding, interleaving, and so on). For example, the teachingsherein may be applied to any one or combinations of the followingtechnologies: Code Division Multiple Access (CDMA) systems,Multiple-Carrier CDMA (MCCDMA), Wideband CDMA (W-CDMA), High-SpeedPacket Access (HSPA, HSPA+) systems, Time Division Multiple Access(TDMA) systems, Frequency Division Multiple Access (FDMA) systems,Single-Carrier FDMA (SC-FDMA) systems, Orthogonal Frequency DivisionMultiple Access (OFDMA) systems, or other multiple access techniques. Awireless communication system employing the teachings herein may bedesigned to implement one or more standards, such as IS-95, cdma2000,IS-856, W-CDMA, TDSCDMA, and other standards. A CDMA network mayimplement a radio technology such as Universal Terrestrial Radio Access(UTRA), cdma2000, or some other technology. UTRA includes W-CDMA and LowChip Rate (LCR). The cdma2000 technology covers IS-2000, IS-95 andIS-856 standards. A TDMA network may implement a radio technology suchas Global System for Mobile Communications (GSM). An OFDMA network mayimplement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11,IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM arepart of Universal Mobile Telecommunication System (UMTS). The teachingsherein may be implemented in a 3GPP Long Term Evolution (LTE) system, anUltra-Mobile Broadband (UMB) system, and other types of systems. LTE isa release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE aredescribed in documents from an organization named “3rd GenerationPartnership Project” (3GPP), while cdma2000 is described in documentsfrom an organization named “3rd Generation Partnership Project 2”(3GPP2). Although certain aspects of the disclosure may be describedusing 3GPP terminology, it is to be understood that the teachings hereinmay be applied to 3GPP (e.g., Re199, Re15, Re16, Re17) technology, aswell as 3GPP2 (e.g., 1xRTT, 1xEV-DO Re10, RevA, RevB) technology andother technologies.

The teachings herein may be incorporated into (e.g., implemented withinor performed by) a variety of apparatuses (e.g., nodes). In someaspects, a node (e.g., a wireless node) implemented in accordance withthe teachings herein may comprise an access point or an access terminal.

For example, an access terminal may comprise, be implemented as, orknown as user equipment, a subscriber station, a subscriber unit, amobile station, a mobile, a mobile node, a remote station, a remoteterminal, a user terminal, a user agent, a user device, or some otherterminology. In some implementations an access terminal may comprise acellular telephone, a cordless telephone, a session initiation protocol(SIP) phone, a wireless local loop (WLL) station, a personal digitalassistant (PDA), a handheld device having wireless connectioncapability, or some other suitable processing device connected to awireless modem. Accordingly, one or more aspects taught herein may beincorporated into a phone (e.g., a cellular phone or smart phone), acomputer (e.g., a laptop), a portable communication device, a portablecomputing device (e.g., a personal data assistant), an entertainmentdevice (e.g., a music device, a video device, or a satellite radio), aglobal positioning system device, or any other suitable device that isconfigured to communicate via a wireless medium.

An access point may comprise, be implemented as, or known as a NodeB, aneNodeB, a radio network controller (RNC), a base station (BS), a radiobase station (RBS), a base station controller (BSC), a base transceiverstation (BTS), a transceiver function (TF), a radio transceiver, a radiorouter, a basic service set (BSS), an extended service set (ESS), amacro cell, a macro node, a Home eNB (HeNB), a femto cell, a femto node,a pico node, or some other similar terminology.

In some aspects a node (e.g., an access point) may comprise an accessnode for a communication system. Such an access node may provide, forexample, connectivity for or to a network (e.g., a wide area networksuch as the Internet or a cellular network) via a wired or wirelesscommunication link to the network. Accordingly, an access node mayenable another node (e.g., an access terminal) to access a network orsome other functionality. In addition, it should be appreciated that oneor both of the nodes may be portable or, in some cases, relativelynon-portable.

Also, it should be appreciated that a wireless node may be capable oftransmitting and/or receiving information in a non-wireless manner(e.g., via a wired connection). Thus, a receiver and a transmitter asdiscussed herein may include appropriate communication interfacecomponents (e.g., electrical or optical interface components) tocommunicate via a non-wireless medium.

A wireless node may communicate via one or more wireless communicationlinks that are based on or otherwise support any suitable wirelesscommunication technology. For example, in some aspects a wireless nodemay associate with a network. In some aspects the network may comprise alocal area network or a wide area network. A wireless device may supportor otherwise use one or more of a variety of wireless communicationtechnologies, protocols, or standards such as those discussed herein(e.g., CDMA, TDMA, OFDM, OFDMA, WiMAX, Wi-Fi, and so on). Similarly, awireless node may support or otherwise use one or more of a variety ofcorresponding modulation or multiplexing schemes. A wireless node maythus include appropriate components (e.g., air interfaces) to establishand communicate via one or more wireless communication links using theabove or other wireless communication technologies. For example, awireless node may comprise a wireless transceiver with associatedtransmitter and receiver components that may include various components(e.g., signal generators and signal processors) that facilitatecommunication over a wireless medium.

The functionality described herein (e.g., with regard to one or more ofthe accompanying figures) may correspond in some aspects to similarlydesignated “means for” functionality in the appended claims. Referringto FIGS. 13-15, apparatuses 1300, 1400, and 1500 are represented as aseries of interrelated functional modules. Here, a module for receivingmessages 1302 or 1404 may correspond at least in some aspects to, forexample, a receiver as discussed herein. A module for identifying aquantity of the messages 1304 may correspond at least in some aspectsto, for example, a controller as discussed herein. A module forcomparing the quantity to a threshold 1306 may correspond at least insome aspects to, for example, a controller as discussed herein. A modulefor ranking access terminals 1404 may correspond at least in someaspects to, for example, a controller as discussed herein. A module fordesignating a subset of the access terminals 1406 may correspond atleast in some aspects to, for example, a controller as discussed herein.A module for controlling transmit power 1308 or 1408 may correspond atleast in some aspects to, for example, a controller as discussed herein.A module for receiving other messages 1310 or 1410 may correspond atleast in some aspects to, for example, a receiver as discussed herein. Amodule for receiving registration messages 1312 or 1412 may correspondat least in some aspects to, for example, a receiver as discussedherein. A module for determining that another access terminal isactively receiving information 1314 or 1414 may correspond at least insome aspects to, for example, a controller as discussed herein. A modulefor restricting transmission 1316 or 1416 may correspond at least insome aspects to, for example, a controller as discussed herein. A modulefor receiving pilot signals 1318 or 1418 may correspond at least in someaspects to, for example, a receiver as discussed herein. A module foridentifying channel conditions 1320 or 1420 may correspond at least insome aspects to, for example, a controller as discussed herein. A modulefor setting at least one limit for the transmit power 1322 or 1422 maycorrespond at least in some aspects to, for example, a controller asdiscussed herein. A module for receiving measurement reports 1502 maycorrespond at least in some aspects to, for example, a receiver asdiscussed herein. A module for determining that an access point controlstransmit power based on measurement reports 1504 may correspond at leastin some aspects to, for example, a controller as discussed herein. Amodule for sending measurement reports to the access point 1506 maycorrespond at least in some aspects to, for example, a transmitter asdiscussed herein. A module for aggregating measurement reports 1508 maycorrespond at least in some aspects to, for example, a controller asdiscussed herein.

The functionality of the modules of FIGS. 13-15 may be implemented invarious ways consistent with the teachings herein. In some aspects thefunctionality of these modules may be implemented as one or moreelectrical components. In some aspects the functionality of these blocksmay be implemented as a processing system including one or moreprocessor components. In some aspects the functionality of these modulesmay be implemented using, for example, at least a portion of one or moreintegrated circuits (e.g., an ASIC). As discussed herein, an integratedcircuit may include a processor, software, other related components, orsome combination thereof. The functionality of these modules also may beimplemented in some other manner as taught herein. In some aspects oneor more of any dashed blocks in FIGS. 13-15 are optional.

It should be understood that any reference to an element herein using adesignation such as “first,” “second,” and so forth does not generallylimit the quantity or order of those elements. Rather, thesedesignations may be used herein as a convenient method of distinguishingbetween two or more elements or instances of an element. Thus, areference to first and second elements does not mean that only twoelements may be employed there or that the first element must precedethe second element in some manner. Also, unless stated otherwise a setof elements may comprise one or more elements. In addition, terminologyof the form “at least one of: A, B, or C” used in the description or theclaims means “A or B or C or any combination of these elements.”

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that any of the variousillustrative logical blocks, modules, processors, means, circuits, andalgorithm steps described in connection with the aspects disclosedherein may be implemented as electronic hardware (e.g., a digitalimplementation, an analog implementation, or a combination of the two,which may be designed using source coding or some other technique),various forms of program or design code incorporating instructions(which may be referred to herein, for convenience, as “software” or a“software module”), or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the aspects disclosed herein may be implementedwithin or performed by an integrated circuit (IC), an access terminal,or an access point. The IC may comprise a general purpose processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, electrical components, optical components,mechanical components, or any combination thereof designed to performthe functions described herein, and may execute codes or instructionsthat reside within the IC, outside of the IC, or both. A general purposeprocessor may be a microprocessor, but in the alternative, the processormay be any conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor, aplurality of microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

It is understood that any specific order or hierarchy of steps in anydisclosed process is an example of a sample approach. Based upon designpreferences, it is understood that the specific order or hierarchy ofsteps in the processes may be rearranged while remaining within thescope of the present disclosure. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

In one or more exemplary embodiments, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium that can be used to carry or store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media. It should beappreciated that a computer-readable medium may be implemented in anysuitable computer-program product.

The previous description of the disclosed aspects is provided to enableany person skilled in the art to make or use the present disclosure.Various modifications to these aspects will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other aspects without departing from the scope of thedisclosure. Thus, the present disclosure is not intended to be limitedto the aspects shown herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed herein.

What is claimed is:
 1. A method of communication, comprising: receivingmessages at an access point, wherein the messages comprise measurementreports from at least one access terminal that is not currently beingserved by the access point; identifying a quantity of the messages thatindicate the occurrence of a specified type of event; comparing thequantity to a threshold; and controlling transmit power of the accesspoint based on the comparison.
 2. The method of claim 1, wherein thespecified type of event comprises a UMTS Event 1A.
 3. The method ofclaim 1, wherein the messages are received from the at least one accessterminal via a network backhaul.
 4. The method of claim 1, wherein: thequantity comprises an observed event count; and the threshold comprisesa target event count.
 5. The method of claim 4, wherein the controllingof the transmit power comprises: determining a power adjustment based ona difference between the target event count and the observed eventcount; and adjusting the transmit power based on determined poweradjustment.
 6. The method of claim 5, wherein the determination of thepower adjustment comprises applying a monotonic non-decreasing functionto the difference between the target event count and the observed eventcount.
 7. The method of claim 1, wherein: the access point comprises afemto cell; and the at least one access terminal is currently beingserved by a macro cell.
 8. The method of claim 1, further comprisingreceiving other messages from at least one access terminal that iscurrently being served by the access point, wherein: the other messagesare indicative of channel quality on a forward link of the access point;and the controlling of the transmit power is further based on the othermessages.
 9. The method of claim 1, further comprising receivingregistration messages at the access point, wherein: the registrationmessages are indicative of a quantity of registration attempts by atleast one access terminal that is not authorized to receive active modeservice via the access point; and the controlling of the transmit poweris further based on the registration messages.
 10. The method of claim1, further comprising: determining that another access terminal near theaccess point is actively receiving information from another accesspoint; and restricting transmission by the access point as a result ofthe determination.
 11. The method of claim 1, further comprising:receiving pilot signals at the access point, wherein the pilot signalsare received from at least one other access point; identifying channelconditions at the access point based on the received pilot signals; andsetting at least one limit for the transmit power based on theidentified channel conditions.
 12. An apparatus for communication,comprising: a receiver operable to receive messages, wherein themessages comprise measurement reports from at least one access terminalthat is not currently being served by the apparatus; and a controlleroperable to identify a quantity of the messages that indicate theoccurrence of a specified type of event, and further operable to comparethe quantity to a threshold, and further operable to control transmitpower of the apparatus based on the comparison.
 13. The apparatus ofclaim 12, wherein the specified type of event comprises a UMTS Event 1A.14. The apparatus of claim 12, wherein the messages are received fromthe at least one access terminal via a network backhaul.
 15. Theapparatus of claim 12, wherein: the quantity comprises an observed eventcount; and the threshold comprises a target event count.
 16. Theapparatus of claim 15, wherein the controlling of the transmit powercomprises: determining a power adjustment based on a difference betweenthe target event count and the observed event count; and adjusting thetransmit power based on determined power adjustment.
 17. The apparatusof claim 16, wherein the determination of the power adjustment comprisesapplying a monotonic non-decreasing function to the difference betweenthe target event count and the observed event count.
 18. The apparatusof claim 12, wherein: the apparatus comprises a femto cell; and the atleast one access terminal is currently being served by a macro cell. 19.The apparatus of claim 12, wherein: the receiver is further operable toreceive other messages from at least one access terminal that iscurrently being served by the apparatus; the other messages areindicative of channel quality on a forward link of the apparatus; andthe controlling of the transmit power is further based on the othermessages.
 20. The apparatus of claim 12, wherein: the receiver isfurther operable to receive registration messages; the registrationmessages are indicative of a quantity of registration attempts by atleast one access terminal that is not authorized to receive active modeservice via the apparatus; and the controlling of the transmit power isfurther based on the registration messages.
 21. The apparatus of claim12, wherein the controller is further operable to: determine thatanother access terminal near the apparatus is actively receivinginformation from an access point; and restrict transmission by theapparatus as a result of the determination.
 22. The apparatus of claim12, wherein: the receiver is further operable to receive pilot signalsfrom at least one access point; the controller is further operable toidentify channel conditions at the apparatus based on the received pilotsignals; and the controller is further operable to set at least onelimit for the transmit power based on the identified channel conditions.23. An apparatus for communication, comprising: means for receivingmessages, wherein the messages comprise measurement reports from atleast one access terminal that is not currently being served by theapparatus; means for identifying a quantity of the messages thatindicate the occurrence of a specified type of event; means forcomparing the quantity to a threshold; and means for controllingtransmit power of the apparatus based on the comparison.
 24. Theapparatus of claim 23, wherein: the quantity comprises an observed eventcount; and the threshold comprises a target event count.
 25. Theapparatus of claim 24, wherein the controlling of the transmit powercomprises: determining a power adjustment based on a difference betweenthe target event count and the observed event count; and adjusting thetransmit power based on determined power adjustment.
 26. The apparatusof claim 25, wherein the determination of the power adjustment comprisesapplying a monotonic non-decreasing function to the difference betweenthe target event count and the observed event count.
 27. The apparatusof claim 23, wherein: the apparatus comprises a femto cell; and the atleast one access terminal is currently being served by a macro cell. 28.The apparatus of claim 23, further comprising: means for determiningthat another access terminal near the apparatus is actively receivinginformation from an access point; and means for restricting transmissionby the apparatus as a result of the determination.
 29. The apparatus ofclaim 23, further comprising: means for receiving pilot signals from atleast one access point; means for identifying channel conditions at theapparatus based on the received pilot signals; and means for setting atleast one limit for the transmit power based on the identified channelconditions.
 30. A computer-program product, comprising:computer-readable medium comprising code for causing a computer to:receive messages at an access point, wherein the messages comprisemeasurement reports from at least one access terminal that is notcurrently being served by the access point; identify a quantity of themessages that indicate the occurrence of a specified type of event;compare the quantity to a threshold; and control transmit power of theaccess point based on the comparison.
 31. The computer-program productof claim 30, wherein: the quantity comprises an observed event count;and the threshold comprises a target event count.
 32. Thecomputer-program product of claim 31, wherein the controlling of thetransmit power comprises: determining a power adjustment based on adifference between the target event count and the observed event count;and adjusting the transmit power based on determined power adjustment.33. The computer-program product of claim 32, wherein the determinationof the power adjustment comprises applying a monotonic non-decreasingfunction to the difference between the target event count and theobserved event count.
 34. The computer-program product of claim 30,wherein: the access point comprises a femto cell; and the at least oneaccess terminal is currently being served by a macro cell.
 35. Thecomputer-program product of claim 30, wherein the computer-readablemedium further comprises code for causing the computer to: determinethat another access terminal near the access point is actively receivinginformation from another access point; and restrict transmission by theaccess point as a result of the determination.
 36. The computer-programproduct of claim 30, wherein the computer-readable medium furthercomprises code for causing the computer to: receive pilot signals at theaccess point, wherein the pilot signals are received from at least oneother access point; identify channel conditions at the access pointbased on the received pilot signals; and set at least one limit for thetransmit power based on the identified channel conditions.
 37. A methodof communication, comprising: receiving measurement reports at a networkentity, wherein each of the measurement reports correspond to aspecified access point; determining that the specified access pointcontrols transmit power based on measurement reports; and sending themeasurement reports to the specified access point as a result of thedetermination.
 38. The method of claim 37, wherein: the measurementreports are received from a plurality of access terminals; the methodfurther comprises aggregating the measurement reports based on which oneof the access terminals sent a given one of the measurement reports; andthe sending of the measurement reports comprises sending the aggregatedmeasurement reports along with indications that identify each subset ofthe measurement reports sent by each of the access terminals.
 39. Themethod of claim 37, wherein the sending of the measurement reports istriggered by a request from the specified access point.
 40. The methodof claim 37, wherein the sending of the measurement reports is performedperiodically.
 41. The method of claim 37, wherein the specified accesspoint comprises a femto cell.
 42. The method of claim 37, wherein thenetwork entity comprises a radio network controller, a Home NodeBmanagement server, or a femto cell.
 43. An apparatus for communication,comprising: a receiver operable to receive measurement reports, whereineach of the measurement reports corresponds to a specified access point;a controller operable to determine that the specified access pointcontrols transmit power based on measurement reports; and a transmitteroperable to send the measurement reports to the specified access pointas a result of the determination.
 44. The apparatus of claim 43,wherein: the measurement reports are received from a plurality of accessterminals; the controller is further operable to aggregate themeasurement reports based on which one of the access terminals sent agiven one of the measurement reports; and the sending of the measurementreports comprises sending the aggregated measurement reports along withindications that identify each subset of the measurement reports sent byeach of the access terminals.
 45. The apparatus of claim 43, wherein thesending of the measurement reports is triggered by a request from thespecified access point.
 46. The apparatus of claim 43, wherein thesending of the measurement reports is performed periodically.
 47. Theapparatus of claim 43, wherein the specified access point comprises afemto cell.
 48. The apparatus of claim 43, wherein the apparatuscomprises a radio network controller, a Home NodeB management server, ora femto cell.
 49. An apparatus for communication, comprising: means forreceiving measurement reports, wherein each of the measurement reportscorrespond to a specified access point; means for determining that thespecified access point controls transmit power based on measurementreports; and means for sending the measurement reports to the specifiedaccess point as a result of the determination.
 50. The apparatus ofclaim 49, wherein: the measurement reports are received from a pluralityof access terminals; the apparatus further comprises means foraggregating the measurement reports based on which one of the accessterminals sent a given one of the measurement reports; and the sendingof the measurement reports comprises sending the aggregated measurementreports along with indications that identify each subset of themeasurement reports sent by each of the access terminals.
 51. Theapparatus of claim 49, wherein the sending of the measurement reports istriggered by a request from the specified access point.
 52. Theapparatus of claim 49, wherein the sending of the measurement reports isperformed periodically.
 53. A computer-program product, comprising:computer-readable medium comprising code for causing a computer to:receive measurement reports at a network entity, wherein each of themeasurement reports corresponds to a specified access point; determinethat the specified access point controls transmit power based onmeasurement reports; and send the measurement reports to the specifiedaccess point as a result of the determination.
 54. The computer-programproduct of claim 53, wherein: the measurement reports are received froma plurality of access terminals; the computer-readable medium furthercomprises code for causing the computer to aggregate the measurementreports based on which one of the access terminals sent a given one ofthe measurement reports; and the sending of the measurement reportscomprises sending the aggregated measurement reports along withindications that identify each subset of the measurement reports sent byeach of the access terminals.
 55. The computer-program product of claim53, wherein the sending of the measurement reports is triggered by arequest from the specified access point.
 56. The computer-programproduct of claim 53, wherein the sending of the measurement reports isperformed periodically.